An explosion at the headquarters of Mexico's state-run oil giant Petroleos Mexicanos (Pemex) has killed 36 people and injured more than 100, according to Reuters. The reasons for the Jan. 31 blast remain unknown.

The explosion occurred at the basement of the administrative building, located in immediate vicinity of the company's 52-story main office tower, where several thousand people were working at the time of the incident. Pemex said it had evacuated about 3,500 people from the damaged building in downtown Mexico City as a precautionary measure, due to a problem with the electricity.

According to witnesses, the lights went out after the explosion and there was debris everywhere. A woman working in the same block as the Pemex building said she heard the explosion and saw white smoke and the windows were blown out. People were running out of the building, she added. Four police helicopters arrived at the scene to help rescue employees, while emergency services were pulling injured people out of the building, all covered in thick dust.

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Several floors of the administrative building have been damaged by the blast. Pemex announced in a statement that it would continue operations and pledged that all of its financial and commercial commitments will be fulfilled on time. The company tweeted that an investigation on the causes of the explosion was underway and warned that any reports of the cause were mere speculation.

One of the biggest Mexican newspapers, El Universal, quoted Moises Flores, leader of one of Pemex's unions, as saying that the blast might have been linked to boilers used to generate power and for air-conditioning.

Recently, a senior company official stated on Pemex's Twitter account that the company had reduced its accident rate over the past few years. Most accidents involving the company have occurred at pipeline and refinery installations. A fire at a pipeline metering center near the Texas border killed 30 workers in September 2012, the largest number of fatalities in a single incident for the company in more than a decade, the Financial Times noted.

The incident happened shortly after Mexican President Enrique Pena Nieto, who took office two months ago, pledged to implement the largest reform in the country's energy industry since Mexico took control over oil fields belonging to British and U.S. companies 75 years ago. Mexico is predicted to grow faster than Brazil for a third consecutive year. Brazil is the only stronger Latin American economy at the moment, according to Bloomberg.